I was running this script with great success in the past, but I just noticed that for a long while I haven't received any more local messages on ssh attempts. Since I don't think they have stopped all of a sudden, I checked my init script and I found this out:

Thanks very much. Your script made me notice where my error was coming from: my log file had changed from /var/log/auth.log to /var/log/messages but I hadn't updated this info in my blacklist.py script.